I’ve been moving Infrastructure of my project to Ef Core 8 from CosmosClient and I’ve been getting exception `System.InvalidOperationException: Nullable object must have a value”, while getting entity that contains List of ValueObjects

My entity:

public sealed class Test : BaseEntity
{
    public string ShortName { get; set; } = null!;
    public string Name { get; set; } = null!;
    public List<Marker> Markers { get; set; } = [];

    public Test(string name, string? shortName = null)
    {
        Name = name;
        ShortName = shortName ?? name;
        Id = ShortName.EncodePolishLetterAndWhiteChars();
    }

    public Test() { }
}

Marker:

public sealed class Marker : BaseEntity
{
    public Marker() { }
    public Marker(string name,
        decimal? lowerNorm = null,
        decimal? upperNorm = null,
        string? unit = null,
        string? shortName = null)
    {
        ShortName = shortName ?? name;
        Name = name;
        LowerNorm = lowerNorm;
        UpperNorm = upperNorm;
        Unit = unit;
    }

    public string ShortName { get; set; } = null!;
    public string Name { get; set; } = null!;
    public decimal? LowerNorm { get; set; }
    public decimal? UpperNorm { get; set; }
    public string? Unit { get; set; }
}

DbContext OnModelCreating:

...
 modelBuilder
            .Entity<Test>()
            .ToContainer("Tests")
            .HasNoDiscriminator()
            .HasPartitionKey(r => r.ShortName);
        modelBuilder.Entity<Test>()
            .Property(r => r.Id)
            .ToJsonProperty("id");
        modelBuilder.Entity<Test>()
            .ComplexProperty(r => r.Markers)
            .IsRequired();
...

I’ve tried making every property nullable, making List nullable and making List of nullable Markers. When I do not set Markers as Complex Property I get Test but List is empty.